US4808095A - Screw vacuum pump - Google Patents

Screw vacuum pump Download PDF

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Publication number
US4808095A
US4808095A US07/108,702 US10870287A US4808095A US 4808095 A US4808095 A US 4808095A US 10870287 A US10870287 A US 10870287A US 4808095 A US4808095 A US 4808095A
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US
United States
Prior art keywords
rotor chamber
helical groove
cooling gas
casing
screw
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US07/108,702
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English (en)
Inventor
Kunihiko Nishitani
Noboru Tsuboi
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Kobe Steel Ltd
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Kobe Steel Ltd
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Filing date
Publication date
Application filed by Kobe Steel Ltd filed Critical Kobe Steel Ltd
Assigned to KABUSHIKI KAISHA KOBE SEIKO SHO reassignment KABUSHIKI KAISHA KOBE SEIKO SHO ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: NISHITANI, KUNIHIKO, TSUBOI, NOBORU
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/04—Heating; Cooling; Heat insulation
    • F04C29/042—Heating; Cooling; Heat insulation by injecting a fluid
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C18/14—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
    • F04C18/16—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C25/00—Adaptations of pumps for special use of pumps for elastic fluids
    • F04C25/02—Adaptations of pumps for special use of pumps for elastic fluids for producing high vacuum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2220/00—Application
    • F04C2220/10—Vacuum
    • F04C2220/12—Dry running

Definitions

  • the present invention relates to a screw vacuum pump having a pair of screw rotors meshed with each other and, more particularly, to an oilless screw pump suitable for application to industries such as the semiconductor industries where air containing foreign matters is detrimental to the products and for application to the industry where odorous air must be avoided.
  • Japanese Patent Publication No. 54-37693 discloses a water-sealed vacuum pump
  • Japanese Patent Publication No. 57-59920 discloses a high-vacuum pump
  • Japanese Patent Provisional Publication (Kokai) No. 59-185889 discloses a dual shaft vacuum pump.
  • the oilless screw vacuum pump is one of the desirable pumps.
  • the screw vacuum pump is of the same construction as the compressor.
  • the compression ratio of the screw vacuum pump namely, the ratio of the pressure of the discharge gas to that of the suction gas, is very high.
  • the discharge pressure of the vacuum pump in general, is atmospheric pressure (1.033 ata), while the suction pressure is on the order of 0.1 ata or 0.01 ata. Consequently, the temperature of the discharge gas is elevated to a very high level due to adiabatic compression of the gas.
  • Discharge gas temperature Td (°K) is expressed by
  • the compression ratio P2/P1 is very large when the suction pressure is on the order of 0.01 or 0.001 torr, and hence the discharge gas temperature Td is elevated to a very high level.
  • the discharge gas temperature Td is 317° C. (590° K.) and 867° C. (1140° K.) when the suction pressure P1 is 0.1 ata (76 torr) and 0.01 ata (7.6 torr), respectively.
  • the vacuum pump exerts a relatively small amount of work on the gas, but elevates the temperature of the gas to a considerably high level.
  • the gas is brought into direct contact with water or oil while the gas flows from the suction port to the discharge port so that the gas and the vacuum pump is cooled.
  • vacuum pump suffers from the leakage of water or oil in the suction side and the reverse flow of water or oil in case the vacuum pump is stopped suddenly or when the power supply is interrupted accidentally. Accordingly, such vacuum pump is inapplicable to the semiconductor industries and the food industries for the above-mentioned reasons.
  • oilless dual shaft vacuum pump which brings the gas in contact with neither water nor oil.
  • "oilless” means not requiring oil or water which is to be brought into contact with the gas while the gas flows through the vacuum pump.
  • the oilless dual shaft vacuum pump is applicable for operation at a vacuum in a medium vacuum range.
  • the rotors of the oilless dual shaft vacuum pump must be positioned with a gap therebetween, the leakage of the gas through the gap between the rotors increases when the oilless dual shaft vacuum pump is applied for operation in a low vacuum range.
  • the present invention has been proposed to solve the above-noted problems in the conventional vacuum pumps.
  • an oilless screw vacuum pump comprises a casing having a rotor chamber having one end opening into a suction port and the other end opening into a discharge port, and cooling gas supply bores formed through the wall of the rotor chamber so as to open into closed spaces in the rotor chamber and so as not to communicate with either the suction port or the dischrge port; and a set of screw rotors rotatably disposed in the rotor chamber so as to be meshed with each other.
  • an oilless screw vacuum pump comprises a casing having a rotor chamber having one end opening into a suction port and the other end opening into a discharge port, and a cooling gas supply bore formed through the wall of the rotor chamber so as to open into the atmosphere and into the rotor chamber at a position where the average pressure of the gas is lower than the pressure of the same at the discharge port; a pair of screw rotors rotatably disposed in the rotor chamber so as to be meshed with each other.
  • a cooling gas is supplied into the fixed rotor wall chamber without using any gas supply means to directly cool the gas being compressed so that a rise in the temperature of the gas is suppressed effectively.
  • FIG. 1 is fragmentary longitudinal sectional view of a screw vacuum pump, in a first embodiment, according to the present invention
  • FIG. 2 is a sectional view taken on line II--II in FIG. 1;
  • FIG. 3 is a fragmentary longitudinal sectional view of a screw vacuum pump, in a second embodiment, according to the present invention.
  • FIG. 4 is a sectional view taken on line IV--IV in FIG. 3;
  • FIG. 5 is a plan view for explaining the positional relationship between the discharge port and the screw rotors of the screw vacuum pump of FIG. 3
  • FIG. 6 is a graph showing pressure distributions inside and outside the rotor chamber of the screw vacuum pump of FIG. 3;
  • FIGS. 7, 8 and 9 are graphs showing general PV diagrams for vacuum pumps.
  • an oilless screw vacuum pump comprising a casing 6 having a rotor chamber 5 and a water jacket 11, and a pair of screw rotors 1 and 2 rotatably disposed in the rotor chamber 5 and meshed with each other.
  • the rotor chamber 5 communicates at one end with a suction passage 3 and at the other end with a discharge passage 4.
  • the helical grooves 9 and 10 of the screw rotors 1 and 2 each sequentially takes on three transient states, namely, a suction state in which the helical groove is open into the suction passage 3, a sealed state in which the helical groove defines a sealed space communicating with neither the suction passage 3 nor the discharge passage 4 between the wall thereof and the inner surface of the rotor chamber 5 and a discharge state in which the helical groove communicates with the discharge passage 4, as the screw rotors 1 and 2 are rotated.
  • the screw vacuum pump 100 has, as a constructional feature specific to screw vacuum pumps, sealed spaces which are always in a sealed state in the rotor chamber 5.
  • Cooling gas supply bores 7 are formed through the wall of the casing 6 so as to open into the sealed spaces, respectively, and into the atmosphere. Air of a temperature (i.e., an ordinary temperature) far lower than that of the gas being compressed in the rotor chamber 5 is supplied through the cooling gas supply bores 7 into the sealed spaces only by the agency of the difference between the atmospheric pressure and the pressure prevailing in the sealed spaces to cool the gas being compressed.
  • the water jacket surrounding the cooling gas supply bores 7 cools the air flowing through the cooling gas supply bores 7 to enhance the cooling effect of the air.
  • the pressure in the sealed spaces of a screw compressor for compressing a gas is higher than the atmospheric pressure. Therefore, it is impossible to supply air into the sealed spaces of the screw compressor only by the pressure difference between the sealed spaces and the atmosphere even if such cooling gas supply bores are formed in the casing.
  • the force supply of air through the cooling gas supply bores into the sealed spaces in the rotor chamber requires an additional device, which increases the power consumption rate of the screw compressor to disadvantage.
  • the cooling effect of the water jacket 11 for cooling the gas and the screw rotors 1 and 2 is insignificant. Since the air supplied into the sealed spaces in the rotor chamber 5 serves as a heat transfer medium, the air supplied into the sealed spaces enhances the cooling effect of the water jacket 11 in addition to directly cooling the gas being compressed by the agency of the temperature difference.
  • the sealed spaces never communicate with the suction passage 3, and the supply of air through the cooling gas supply bores 7 into the sealed spaces never affects the vacuum on the side of the suction passage 3.
  • a flow regulating device such as a needle valve, may be provided at the entrance of the cooling gas supply bore 7 to regulate the flow rate of air through the cooling gas supply bore 7.
  • an oilless screw vacuum pump 200 incorporates a further improvement.
  • the oilless screw vacuum pump 200 comprises a casing 6 having a rotor chamber 5 having one end communicating with a suction passage 3 and the other end communicating with a discharge passage 4, and a pair of screw rotors 1 and 2 rotatably disposed in the rotor chamber 5 and meshed with each other.
  • a cooling gas supply bore 7 is formed through the wall of the casing 6.
  • the cooling gas supply bore 7 has one end opening into the atmosphere and the other end opening into the rotor chamber 5 at a position A which communicates with the discharge passage 4 and at which the average pressure of the gas is lower than the pressure of the gas prevailing in the discharge passage 4. More particularly, the other end of the cooling gas supply bore 7 opens into the rotor chamber 5 at a position in a shaded section shown in FIG. 5, where the boundary between the respective grooves 9 and 10 of the screw rotors 1 and 2 on the side of the discharge passage 4 coincides with the discharge port 8 (FIG. 5).
  • the degree of diminution in the reachable vacuum is smaller when the cooling gas supply bore 7 is formed at the position A than when the cooling gas supply bore 7 is formed at a position C which is nearer to the suction passage 3 than the position A, because the air supplied into the sealed space must pass more barriers than those in a range from the position C to the suction passage 3 in flowing from the position A to the suction passage 3.
  • FIG. 6 shows the pressure distribution in the rotor chamber 5, in which pressure P is measured on the vertical axis and the distance L from the end surface of the rotors on the discharge side is measured on the horizontal axis.
  • pressure in a range ⁇ L corresponding to the shaded area in FIG. 5 is lower than the atmospheric pressure, so that cooling air is able to flow through the cooling gas supply bore 7 into the rotor chamber 5.
  • air under atmospheric pressure namely, 760 torr
  • the pressure P3 is far lower than the atmospheric pressure, air is able to flow through the cooling gas supply bore 7 into the rotor chamber 5.
  • the cooling gas supply bore 7 is formed at a farthest possible position from the suction passage 3 and allows the spontaneous flow of air through the cooling gas supply bore 7 into the rotor chamber 5 to suppress the leakage of the air into the suction passage 3.
  • FIGS. 7 to 9 are PV diagrams for screw vacuum pumps which are different from each other with respect to the position of the cooling gas supply bore 7, in which the volume V of spaces defined by the grooves of the screw rotors is measured on the horizontal axis and pressure P in the spaces defined by the grooves of the screw rotors is measured on the vertical axis.
  • shaded areas including double shaded areas represent necessary power of the vacuum pumps.
  • FIGS. 7, 8 and 9 are for a screw vacuum pump without the cooling gas supply bore 7, a screw vacuum pump having the cooling gas supply bore 7 at the position A, and a screw vacuum pump having the cooling gas supply bore 7 at the position B.
  • V A and V B indicate the volumes of the gas at the positions A and B, respectively.
  • the PV characteristics of a screw vacuum pump having the cooling gas supply bore 7 at the position C is similar to those of the screw vacuum pump having the cooling gas supply bore 7 at the position B, and hence a description thereof is omitted.
  • cooling gas supply bore 7 is provided only on the side of the screw rotor 2 in the second embodiment, two cooling gas supply bores may be formed on both sides of the screw rotors 1 and 2 or more than two cooling gas supply bores may be formed in the casing.
  • the cooling gas to be supplied through the cooling gas supply bore 7 is not limited to air; any suitable gas may be supplied through the cooling gas supply bore 7.
  • any suitable gas may be supplied through the cooling gas supply bore 7.
  • an inflammable gas such as methanol gas or acetone gas, nitrogen gas or the like may be supplied through the cooling gas supply bore 7 to prevent an explosion in addition to lowering the temperature of the discharged gas.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
US07/108,702 1987-07-01 1987-10-15 Screw vacuum pump Expired - Lifetime US4808095A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP62-165042 1987-07-01
JP62165042A JPS6412092A (en) 1987-07-01 1987-07-01 Vacuum pump of screw type

Publications (1)

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US4808095A true US4808095A (en) 1989-02-28

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US (1) US4808095A (enrdf_load_stackoverflow)
JP (1) JPS6412092A (enrdf_load_stackoverflow)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4984974A (en) * 1987-12-18 1991-01-15 Hitachi, Ltd. Screw type vacuum pump with introduced inert gas
WO1998057067A1 (de) * 1997-06-11 1998-12-17 Sterling Fluid Systems (Germany) Gmbh Schraubenspindelvakuumpumpe und verfahren zum betrieb derselben
US6599097B2 (en) * 2001-08-14 2003-07-29 Woosung Vacuum Co., Ltd. Dry vacuum pump with improved gas discharging speed and pump cooling
US20120063917A1 (en) * 2009-04-17 2012-03-15 Oerlikon Leybold Vacuum Gmbh Roughing pump method for a positive displacement pump
US20120201708A1 (en) * 2009-07-10 2012-08-09 Robuschi S.P.A. Dry screw driver
CN104500400A (zh) * 2014-10-20 2015-04-08 西安交通大学 一种螺杆压缩机气缸的窄缝状喷液结构
CN106089725A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 用于检测消音效果的增压装置
CN106089722A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 汽车发动机用的消音管检测设备
CN106089720A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 阻性消音器气密性的检查装置
CN106089721A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 发动机降噪元件的质检系统
CN106089727A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 用于沙漠越野车的消音系统检测设备
US20170298938A1 (en) * 2014-09-10 2017-10-19 Atlas Copco Airpower, Naamloze Vennootschap Screw compressor element
US10975867B2 (en) 2015-10-30 2021-04-13 Gardner Denver, Inc. Complex screw rotors
US20240218879A1 (en) * 2021-04-30 2024-07-04 Edwards Limited Stator for a vacuum pump

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US958345A (en) * 1910-01-22 1910-05-17 Connersville Blower Co Vacuum-pump.
US1191423A (en) * 1913-01-15 1916-07-18 H & S Pump Company Pump.
US3112869A (en) * 1960-10-17 1963-12-03 Willis A Aschoff High vacuum pump
US3430848A (en) * 1966-02-23 1969-03-04 Plessey Co Ltd Rotary-displacement compressors
US3574488A (en) * 1968-04-19 1971-04-13 Plenty & Son Ltd Screw pumps
US4005949A (en) * 1974-10-10 1977-02-01 Vilter Manufacturing Corporation Variable capacity rotary screw compressor
DE2755328A1 (de) * 1977-03-08 1978-09-14 Leybold Heraeus Sogev Oelgedichtete vakuumpumpe
JPS5759920A (en) * 1980-09-29 1982-04-10 Hiroaki Egawa Photocrosslinkable resin composition
US4329126A (en) * 1977-11-11 1982-05-11 Kobe Steel Limited Method for preventing a leakage loss of gases in a screw compressor
JPS59185889A (ja) * 1983-04-02 1984-10-22 ライボルト−ヘレ−ウス・ゲゼルシヤフト・ミツト・ベシユレンクテル・ハフツング ２軸式真空ポンプ
US4714418A (en) * 1984-04-11 1987-12-22 Hitachi, Ltd. Screw type vacuum pump
US4727725A (en) * 1985-05-20 1988-03-01 Hitachi, Ltd. Gas injection system for screw compressor
JPH01202413A (ja) * 1988-02-09 1989-08-15 Dainippon Ink & Chem Inc 射出成形品の仕上げ方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5675994A (en) * 1979-11-21 1981-06-23 Hitachi Ltd Multieffect screw compressor
JPH0756276B2 (ja) * 1985-10-07 1995-06-14 株式会社神戸製鋼所 オイルフリー形スクリュ式真空ポンプ
JPS6336085A (ja) * 1986-07-30 1988-02-16 Taiko Kikai Kogyo Kk スクリユウ型真空ポンプ

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US958345A (en) * 1910-01-22 1910-05-17 Connersville Blower Co Vacuum-pump.
US1191423A (en) * 1913-01-15 1916-07-18 H & S Pump Company Pump.
US3112869A (en) * 1960-10-17 1963-12-03 Willis A Aschoff High vacuum pump
US3430848A (en) * 1966-02-23 1969-03-04 Plessey Co Ltd Rotary-displacement compressors
US3574488A (en) * 1968-04-19 1971-04-13 Plenty & Son Ltd Screw pumps
US4005949A (en) * 1974-10-10 1977-02-01 Vilter Manufacturing Corporation Variable capacity rotary screw compressor
DE2755328A1 (de) * 1977-03-08 1978-09-14 Leybold Heraeus Sogev Oelgedichtete vakuumpumpe
US4329126A (en) * 1977-11-11 1982-05-11 Kobe Steel Limited Method for preventing a leakage loss of gases in a screw compressor
JPS5759920A (en) * 1980-09-29 1982-04-10 Hiroaki Egawa Photocrosslinkable resin composition
JPS59185889A (ja) * 1983-04-02 1984-10-22 ライボルト−ヘレ−ウス・ゲゼルシヤフト・ミツト・ベシユレンクテル・ハフツング ２軸式真空ポンプ
US4714418A (en) * 1984-04-11 1987-12-22 Hitachi, Ltd. Screw type vacuum pump
US4727725A (en) * 1985-05-20 1988-03-01 Hitachi, Ltd. Gas injection system for screw compressor
JPH01202413A (ja) * 1988-02-09 1989-08-15 Dainippon Ink & Chem Inc 射出成形品の仕上げ方法

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4984974A (en) * 1987-12-18 1991-01-15 Hitachi, Ltd. Screw type vacuum pump with introduced inert gas
WO1998057067A1 (de) * 1997-06-11 1998-12-17 Sterling Fluid Systems (Germany) Gmbh Schraubenspindelvakuumpumpe und verfahren zum betrieb derselben
US6599097B2 (en) * 2001-08-14 2003-07-29 Woosung Vacuum Co., Ltd. Dry vacuum pump with improved gas discharging speed and pump cooling
US20120063917A1 (en) * 2009-04-17 2012-03-15 Oerlikon Leybold Vacuum Gmbh Roughing pump method for a positive displacement pump
US9017040B2 (en) * 2009-04-17 2015-04-28 Oerlikon Leybold Vacuum Gmbh Roughing pump method for a positive displacement pump
US20120201708A1 (en) * 2009-07-10 2012-08-09 Robuschi S.P.A. Dry screw driver
US20170298938A1 (en) * 2014-09-10 2017-10-19 Atlas Copco Airpower, Naamloze Vennootschap Screw compressor element
US10371149B2 (en) * 2014-09-10 2019-08-06 Atlas Copco Airpower, Naamloze Vennootschap Screw compressor element
CN104500400A (zh) * 2014-10-20 2015-04-08 西安交通大学 一种螺杆压缩机气缸的窄缝状喷液结构
US12110888B2 (en) 2015-10-30 2024-10-08 Industrial Technologies And Services, Llc Complex screw rotors having multiple helical profiles joined by a centeral portion with a pocket
US11644034B2 (en) 2015-10-30 2023-05-09 Gardner Denver, Inc. Complex screw rotors
US10975867B2 (en) 2015-10-30 2021-04-13 Gardner Denver, Inc. Complex screw rotors
CN106089721A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 发动机降噪元件的质检系统
CN106089720B (zh) * 2016-08-11 2018-06-26 四川行之智汇知识产权运营有限公司 阻性消音器气密性的检查装置
CN106089721B (zh) * 2016-08-11 2018-06-26 四川行之智汇知识产权运营有限公司 发动机降噪元件的质检系统
CN106089725B (zh) * 2016-08-11 2018-06-26 四川行之智汇知识产权运营有限公司 用于检测消音效果的增压装置
CN106089727A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 用于沙漠越野车的消音系统检测设备
CN106089720A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 阻性消音器气密性的检查装置
CN106089722A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 汽车发动机用的消音管检测设备
CN106089725A (zh) * 2016-08-11 2016-11-09 成都陵川常友汽车部件制造有限公司 用于检测消音效果的增压装置
US20240218879A1 (en) * 2021-04-30 2024-07-04 Edwards Limited Stator for a vacuum pump

Also Published As

Publication number Publication date
JPH045836B2 (enrdf_load_stackoverflow) 1992-02-03
JPS6412092A (en) 1989-01-17

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